Are the things I am suffering from—dreams of jinn, fever, lethargy, an unwillingness to do anything, and neglecting prayer—due to sorcery or envy, or are they mere delusions?

Legitimate Ruqyah (definition) and supplication are two means to get rid of evils, and they are prescribed for both the afflicted and the un-afflicted. Combining prayers without a legitimate excuse is a great evil and a major sin. Allah has warned those who do so in His Almighty saying: "So woe to those who pray [but] are heedless of their prayer" (Al-Ma'un: 4-5), and His saying: "Then succeeded them a generation who neglected prayers and pursued desires; so they are going to meet evil" (Maryam: 59). Thus, each prayer has a specific time, as Allah the Almighty says: "Indeed, prayer has been decreed upon the believers a book [i.e., obligation] of specified times" (An-Nisa: 103).